2 K photoluminescence of indirect GAP Al xGa 1− xAs alloys grown under near-equilibrium conditions by LPE

Abstract

Non-intentionally doped Al x Ga 1− x As epitaxial layers with 0.38≤ x≤0.84 were grown on (100) GaAs substrates by liquid-phase epitaxy under near-equilibrium conditions. Making use of photoluminescence measurements at 2 K it was possible to report, breaking down the spectra into multiple gaussians, the quadratic relationship that followed by the indirect bound exciton line, the free electron–acceptor transition and the recombination of donor–acceptor pair with the increase of the aluminum content. The behavior of the intensity of both bound exciton and donor–acceptor transitions is explained from the evolution of the layer thickness according to the aluminum composition, given that all the samples were grown under the same conditions with fixed growth time. It is also possible to observe the excitonic transition corresponding to the Al x Ga 1− x As/GaAs interface, despite the lattice mismatch and other inconveniences, which are involved when growth high aluminum content with this technique. A very narrow new line (2.8 meV) can be observed in the energetic region of deep levels and defects: 1.0385 eV, whose origin is being studied.